Exotic zebra mussels (ZM) often dominate littoral benthic environments in Midwestern US lakes. We hypothesized that ZM-colonized sediments in the littoral zone (+ZM littoral) would exhibit higher rates of nitrification and denitrification than littoral sediments without zebra mussels (-ZM littoral) and sediments in the profundal zone. To address this hypothesis, we measured nitrification and denitrification on +ZM littoral sediments, and compared them to rates measured from sediments collected along -ZM transects that extended from the littoral to the profundal zone in Gull Lake, Michigan.  Nitrification and denitrification rates were significantly different in sediments from profundal, -ZM littoral, and +ZM littoral collection sites (ANOVA, p = 0.002; p < 0.001, respectively).  Profundal sediments had the lowest nitrification and denitrification rates (0.39 and 0.043 mgN gAFDM^-1 d^-1, respectively), and +ZM littoral sediments had the highest rates (2.64 and 1.31 mgN gAFDM^-1 d^-1, respectively).  Nitrification and denitrification rates were scaled to the entire lake based on relationships among sediment characteristics, water depth, and ZM distribution in littoral and profundal habitats.  Results suggest that ZM may not increase the total N transformation rates in the lake as a whole, but they do produce hot spots of nitrification and denitrification in littoral sediments.